Peptides having an antihypertensive effect

ABSTRACT

Novel peptide derivatives and a method of preparing the same are described. These compounds are useful in the diagnosis and treatment of hypertension.

The present invention relates to new peptide derivatives having antihypertensive activity and to a process for their manufacture.

German Offenlegungsschrift No. 2,323,322 teaches that peptides of formula

    X--Arg--Val--Tyr--Ile--His--Pro--Phegly--OH

in which X is a radical of an aliphatic carboxylic acid having up to 5 carbon atoms which may carry COOH--, CONH₂ --, NH₂ -- or carbo-benzoxy-amino (NHZ) groups or a phthalic acid radical, and Phegly--OH is the L--C--phenyl glycine residue, are antagonists of angiotensin II (AT II).

It has now been found that peptides of formula I

    y--arg--Val--Tyr--Val--His--Pro--Phegly--OH                (I)

in which Y stands for the sarcosyl, succinamoyl or succinoyl radical, have a longer and stronger action as antagonists of angiotensin II than the above-cited known compounds.

Hence, the present invention relates to peptides of formula I with Y defined as above.

This invention further relates to a process for the manufacture of these compounds, which comprises condensing or reacting an N-protected sarcosine or succinic acid monoamide or anhydride with a peptide of formula II

    h--arg--Val--Tyr(Bu.sup.t)--Val--His--Pro--Phegly--OBu.sup.t(II)

and splitting off the protective groups by a treatment with an acid.

The present invention moreover relates to pharmaceutical composition containing an effective amount of a compound of formula I, as well as to a method for preparing such a pharmaceutical composition.

As N-protective group, the tert.-butyloxy carbonyl radical (Boc) which is capable of being split off, as are the protective groups in peptide II, by treatment with an acid, for example tri-fluoroacetic acid or hydrochloric acid in dioxan or acetic acid, is preferably suitable. Further protective groups are, for example, the α,α-dimethyl-3,5-dimethoxy-benzyloxy-carbonyl (Ddz), o-nitrophenyl sulfenyl(NPS) or trityl group.

For formation of the bond between the reaction components, all of the conventional methods of peptide chemistry may be used. Dicyclo-hexyl carbodiimide (DCC), optionally in the presence of N-hydroxy succinimide or 1-hydroxy benzotriazole or analogous compounds as mentioned in Chem. Ber. 103, (1970), page 788, is preferably used. It is also possible to use activated esters of sarcosin or succinic acid, for example with 4-nitrophenol, 2,4,5-trichlorophenol, pentachlorophenol, N-hydroxy-succinimide and similar compounds. When trichloro or nitrophenyl esters are used, the aminolysis may substantially be accelerated by adding acidic N-hydroxy compounds, for example those mentioned in "Chemistry and Biology of Peptides," Ed. Meienhofer, Ann. Arbor Science Publishers, (1972), pages 343 to 350. Especially useful catalysts are, for example, 1-hydroxy-benzotriazole and 2-hydroxy pyridine. As solvents, for example dimethylformamide, dimethylacetamide, phosphoric acid tris-dimethylamide or dimethyl sulfoxide, optionally in admixture with one another, may be mentioned. The succinoyl derivative may also be prepared using the anhydride as an activated compound. For this reaction, pyridine is also suitable as a solvent.

The protective groups are cleft from the reaction products by treatment with an acid, for example trifluoroacetic acid or about 1.5N hydrochloric acid in glacial acetic acid or 3 to 6N hydrochloric acid in dioxan.

The compounds of the invention are diagnostic agents for the differential diagnosis of hypertonia and for the treatment of renin-angiotensin-induced forms of hypertonia.

Apart from being superior to the above-cited angiotensin II peptides, the compounds of the invention are also superior to angiotensin inhibitors, such as [1-sarcosine,5-valine, 8-alanine] angiotensin II, known to be highly active.

Thus, the following data relating to the potency and duration of the antagonistic activity were found:

    __________________________________________________________________________                                   duration                                                      Inhibiting effect in percent                                                                    of action                                                      0.5mcg/kg                                                                            1mcg/kg                                                                             2mcg/kg                                                                             in min.                                                       i.v.   i.v. i.v. 0.1mg/kg                                         Peptide      AT II  AT II                                                                               AT II                                                                               i.v.                                             __________________________________________________________________________     [Suc.sup.1,Val.sup.5 pgl.sup.8 ] AT II                                                      98     94   92   89±22                                         10mcg/kg/min i.v.                                                                           98     94   92                                                    5 "          88     94   93                                                    1 "          42     51   55                                                    [Sar.sup.1,Val.sup.5 Ala.sup.8 ] AT II                                                                       66±21                                         10mcg/kg/min i.v.                                                                           88     90   89                                                    5 "          63     76   75                                                    1 "           0     22   31                                                    [Suc.sup.1, Ile.sup.5,Pgl.sup.8 ]AT II                                                                       51±8                                          10mcg/kg/min i.v.                                                                           40     89   92                                                    5 "          33     52   64                                                    1 "          15      0   13                                                    __________________________________________________________________________      Suc = succinamoyl, Pgl = Phegly (= C-phenyl glycine)                           Sar = Sarcosyl?                                                                Potency and duration of action of [Sar.sup.1, Val.sup.5, Pgl.sup.8 ]AT II      are within the range of the figures for the Suc.sup.1 - analog.?         

The potency of the AT II analogs is determined by measuring the increase in blood pressure caused by increasing amounts of AT II with and without infusion of the analog to be tested, at different dosages; duration of action is determined on the basis of the time during which a single injection of the analog to be tested is effective under permanent infusion of AT II.

This finding is surprising, for all experiments hitherto have shown valine and isoleucine in position 5 of AT II to be completely equivalent, as summerized in Pharmacol. Reviews 26 (1974), page 97, last paragraph. Hence, the superior effect of the new peptides of the invention was not foreseeable.

The peptides of the invention are administered in the form of pharmaceutical compositions. Such a composition, for example for diagnostic purposes, may be in the form of an aqueous solution or of a lyophilized product.

Such an aqueous solution contains, as single dose in 1 - 2 ml., 6 to 100 mcg of angiotensin antagonist. Isotonicity is achieved with NaCl. For preservation, 0.05 - 2 % of a preserving agent, for example phenol, benzyl alcohol, trichloroisobutanol or 4 -hydroxy-benzoic acid ester (methyl or ethyl ester) are added. The solutions are filled into ampules or bottles of 1 - 2 ml capacity.

The composition of the invention in freeze-dried form contains, in addition to the angiotensin antagonist (6 - 100 mcg per single dose), an inert carrier, for example mannitol or sorbitol, and sufficient NaCl to yield an isotonic solution. The composition is freeze-dried in ampules or bottles. For administration, the composition is dissolved in 1 - 2 ml of bi-distilled water.

If a composition is to be used in the treatment of malign hypertonia by continuous drop infusion, the contents of an ampule of 100 mcg of the angiotensin antagonist are dissolved in 500 ml of a physiological salt solution and this solution is administered intravenously at a speed of about 0.5 ml per minute.

In the therapy of hypertonia, compositions are preferred having a prolonged period of action.

Compositions with prolonged action are obtained by preparing zinc complex compounds of the peptides. The most advantageous method for preparing them consists in precipitating these complex compounds together with an excess of zinc ions, for example zinc chloride or zinc sulfate, if necessary in the presence of phosphate, by adjusting the pH-value to about 7.2 - 9, in the form of a mixture with basic zinc hydroxide or zinc phosphate. Before preparing this suspension, the angiotensin-antagonist is dissolved in water at a pH-value below 6, whereupon an about 5 - 100-fold quantity of zinc chloride or of another zinc salt, for example the sulfate, and the about 5 - 40 fold quantity by weight of di-sodium phosphate may be added. The pH-value is then adjusted with 1N-NaOH to about 7.2 to 9, preferably 7.5 to 8.5.

For producing isotonicity, the required quantity of a substance usually employed for this purpose, for example NaCl, KCl, sodium phosphate or sorbitol, mannitol or lactose is added, and the volume adjusted with distilled water. The water contains preserving agents, for example benzyl alcohol, phenol, a 4-hydroxy-benzoic acid ester or trichloro-isobutanol in an amount of 0.05 to about 2%, in order to assure sterility of the preparation. 1 ml of the composition contains as single dose about 50 - 500 mcg of an angiotensin antagonist. The activity period of the complex is many times longer than that of the free hormone.

An angiotensin antagonist having protracted action may also be obtained by combining

a. an aqueous solution of the angiotensin antagonist,

b. an aqueous solution of a gelatin derivative cross-linked with hexamethylene-diisocyanate and prepared according to the method described in German Pat. Nos. 1,118,792 or 1,155,134 (hereinafter referred to as "gelatin derivative"), and

c. a neutral aqueous solution of polyphloretin phosphate, and, if desired, lyophilizing the solution so obtained.

The preparation of polyphloretin phosphate is described in German Pat. No. 929,664, Examples 1, 4 and 5.

For preparing depot compositions, the individual components may be dissolved separately in water and the acidic solution of polyphloretin phosphate is neutralized with an inorganic base such as KOH, NaOH or NH₃ or with an organic base, for example triethylamine, N-ethyl-piperidine or an amino acid amide.

At first, the solution of the angiotensin antagonist and that of the gelatin derivative are combined, and subsequently, the solution of polyphloretin phosphate is added. Isotonicity is achieved with NaCl or with a physiologically acceptable organic compound, for example an amino acid such as sodium glutamate, and the pH-value of the solution is adjusted to 5.5 to 7.5, preferably 6.5 to 7.0. The solution is filtered under sterile conditions, filled into ampules or bottles under sterile conditions and, if desired, freeze-dried.

A single dose contains about 50 - 500 mcg of one of the angiotensin-antagonists of the invention, whilst the daily dosage ranges from about 1 to 10 mg.

Polyphloretin phosphate and the gelatin derivative are preferably used in a greater excess, that is at least the 20-fold and at most about the 500-fold quantity by weight. The compounds of the invention do not consist of simple mixtures of the components. This is proved by the fact that, for example the specific extinction of the angiotensin antagonist at 270 - 285 mμ is reduced to about half its value upon addition of the gelatin derivative, which is a sure sign for the formation of a complex compound with modified steric structure. The duration of action of the complex compound is many times that of the free hormone.

The following Examples illustrate the invention. The composition is manufactured according to methods known to the expert within the scope given above.

EXAMPLE 1 a. Z--Val--Tyr(Bu^(t))OCH₃

46 Grams (0.16 mol) of H--Tyr(Bu^(t))OCH₃ . HCl were dissolved in 180 ml of dimethylformamide, the solution was cooled to 0° C, and 20.2 ml (0.16 mol) of N-ethyl morpholine were added. A solution of 40 g (0.16 mol) of Z--Val--OH and 21.6 g (0.16 mol) of 1-hydroxy benzotriazole in 150 ml of dimethylformamide was then added. While stirring at -5° C, a solution of 36.4 g (0.16 mol) of dicyclohexyl carbodiimide in 5 ml of dimethylformamide was admixed. Stirring was continued for 3 hours at 0° C and then for 3 hours at room temperature. After standing overnight at +4° C, the dicyclohexyl urea which had precipitated was separated by suction-filtration. The filtrate was concentrated at room temperature under greatly reduced pressure until it had an oily consistency. It was dissolved in ethyl acetate and the ethyl acetate solution successively washed with sodium bicarbonate solution, a 5% potassium bisulfate solution and water, dried over sodium sulfate, clarified by means of charcoal and concentrated in vacuo to yield an oil. It was dissolved in 150 ml of absolute ether with heating, and after cooling, the product was precipitated by means of 3 l of low-boiling petroleum ether. The precipitate was suction-filtered after having stood overnight at +4° C, and dried in vacuo over P₂ O₅.

Yield: 715 g (92% of the theoretical yield), [α]_(D) = -16.2° (c = 1, CH₃ OH).

b. Z--Val--Tyr(Bu^(t))--OH

68 Grams of Z--Val--Tyr(Bu^(t))--OCH₃ were dissolved in a mixture of 350 ml of dioxan and 150 ml of water. While controlling the pH-value electrometrically (pH>12), 140 ml of 1N sodium hydroxide solution were slowly added. After saponification was complete, the solution was neutralized by means of 1N HCl, concentrated in vacuo to a small volume and acidified to pH 3 by means of hydrochloric acid. The precipitate was suction-filtered, washed with water and dried in vacuo.

Yield: 65.7 g, m.p. 116° C, [α]_(D) = -5.2° (c = 1, CH₃ OH).

c. Z--Val--His--OCH₃

With exclusion of moisture, a solution of 42 g of dicyclohexyl carbodiimide in 60 ml of dimethylformamide was added at 0° C to a solution of 50.2 g (0.2 mol) of Z--Val--OH and 27 g (0.2 mol) of 1-hydroxy benzotriazole in 200 ml of dimethyl-formamide. Stirring was continued for 90 minutes at 0° C and then for 90 minutes at room temperature, the separated dicyclo-hexyl urea was suction-filtered and the filtrate was added to a solution obtained by dissolving with cooling 60 g of H--His--OCH₃ . 2 HCl (80% pure, 0.2 mol) and 60.8 ml of N-ethyl morpholine in 250 ml of dimethyl sulfoxide. After standing for 24 hours at room temperature, the precipitate was suction-filtered. The filtrate was concentrated in vacuo at room temperature to an oil which was triturated three times with 500 ml each of absolute ether, and the oily residue was stirred with saturated aqueous sodium carbonate solution. The solidified product was stirred with bicarbonate solution and subsequently with water and dried in vacuo.

Yield: 50.2 g, m.p. 169° - 170° C.

After reprecipitation from dimethylformamide/ether/petroleum ether, 49 g of product were obtained of m.p. 168° - 170° C; [α]_(D) = +5.6° (c = 1, DMF).

d. Z--Val--His--OH

48.8 Grams (0.121 mol) of Z--Val--His--OCH₃ were suspended in 700 ml of dioxan, 0.1 ml of a 1% ethanolic thymol phthalein solution was added while stirring, and in 3 successive portions (each added upon colour change of the indicator) a total of 123 ml of 1N NaOH was added. When saponification was complete, the solution was neutralized by means of 2N HCl, concentrated in vacuo at room temperature to a small volume and acidified to pH 3.0 by means of normal HCl. The precipitated oily substance solidified in an ice bath and was suction-filtered, washed with water and triturated with a small amount of ethyl acetate.

Yield: 36.4 g, m.p. 155° C, [α]_(D) = + 27.2° (c = 1, CH₃ OH).

e. Z--Val--His--Pro--Phegly--OBu^(t)

1.9 Milliliters (0.015 mol) of N-ethyl morpholine were added at 0° C to a solution of 5.1 g (0.015 mol) of H--Pro--Phegly--OBu^(t) . HCl, prepared according to German Offenlegungsschrift No. 2,323,322, in 35 ml of dimethylformamide, and the mixture was combined with a solution of 5.8 g (0.015 mol) of Z--Val--His--OH and 2.1 g of 1-hydroxy benzotriazole (0.015 mol) in 50 ml of dimethylformamide. While stirring at -5° C, a solution of 3.4 g of dicyclohexyl carbodiimide in 5 ml of dimethylformamide was admixed. Stirring was continued for 1 hour at 0° C and overnight at room temperature. The separated dicyclohexyl urea was suction-filtered, and the solvent was distilled off in vacuo at room temperature. The residue was dissolved in 250 ml of ethyl acetate, the ethyl acetate solution was washed with sodium carbonate solution and water, dried over magnesium sulfate, and after clarification with charcoal, concentrated in vacuo at room temperature to a small volume, and the product was finally precipitated with dry diethyl ether.

Yield: 8.5 g, m.p. 124° C; [α]_(D) = -17.0° (c = 1, CH₃ OH).

f. H--Val--His--Pro--Phegly--OBu^(t) . 2 HCl

8.3 Grams of Z--Val--His--Pro--Phegly--OBu^(t) were dissolved in 200 ml of CH₃ OH, 3 g of a 10% Pd/BaSO₄ catalyst were added, and the mixture was hydrogenated while stirring, with the exclusion of air, by passing hydrogen through it. The pH-value was maintained at 3.0 by adding dropwise 1N methanolic HCl. After suction-filtration of the catalyst, concentration of the solution in vacuo and precipitation of the product with dry diethyl ether, 7.1 g of a product were obtained; m.p. 170° C (with decomposition), [α]_(D) = -17.8° (c = 1, CH₃ OH).

g. Z--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t)

18.63 Grams (0.05 mol) of Z--Tyr(Bu^(t))--OH and a solution of 11.3 g (0.05 mol) of dicyclohexyl carbodiimide in 16 ml of dimethyl-formamide were added successively at 0° C to a solution prepared at 0° C from 30.6 g (0.05 mol) of H--Val--His--Pro--Phegly--OBu^(t) . 2 HCl and 12.6 ml (0.1 mol) of N-ethyl morpholine in 100 ml of dimethylformamide. Stirring was then continued for 1 hour at 0° C and for 16 hours at room temperature. The separated dicyclohexyl urea was suction-filtered, the solvent was distilled off, and the product was dissolved in ethyl acetate. The solution was washed with saturated aqueous sodium bicarbonate solution and water, dried over sodium sulfate, clarified with charcoal and concentrated in vacuo at room temperature. 44.1 Grams of a nearly colorless, amorphous solid were obtained, m.p. 109° C (decomposition), [α]_(D) = -15.5° (c = 1, CH₃ OH).

h. H--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t) . 2 HCl

44 Grams of Z--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t) were dissolved in 850 ml of CH₃ OH, and the solution was hydrogenated as in (f). After distillation of the solvent, the product was obtained as a colorless, amorphous solid.

Yield: 38.4 g, m.p. 114° C, [α]_(D) = + 4.8° (c = 1, CH₃ OH).

i. Z--Val--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t)

38 Grams (0.04 mol) of H--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t) and 10.12 ml (0.09 mol) of N-ethyl morpholine were dissolved at 0° C in 280 ml of dimethylformamide, then a solution of 10.1 g (0.04 mol) of Z--Val--OH and 5.4 g (0.04 mol) of 1-hydroxy benzotriazole in 80 ml of dimethylformamide was admixed. After cooling to -5° C, 9.1 g of dicyclohexyl carbodiimide dissolved in 15 ml of dimethylformamide were added. Stirring was continued for 1 hour at 0° C and for 16 hours at room temperature. After the precipitated dicyclohexyl urea had been separated, and the solvent had been distilled off in vacuo at room temperature, the residue was dissolved in ethyl acetate, the solution was washed with a 2N sodium carbonate solution, dried with sodium sulfate, clarified with charcoal, and the product was isolated by distilling off the solvent and trituration with absolute diethyl ether.

Yield: 31.7 g, m.p. 155° C (decomposition), [α]_(D) = -14.8° (c = 1, DMF).

k. H--Val--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t) . 2 HCl

A solution of 31.5 g of Z--Val--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t) in 600 ml of methanol was hydrogenated as sub (f) and worked up.

Yield: 28.6 g, m.p. 183° C, [α]_(D) = +9.6° (c = 1, DMF).

l. Z₃ Arg--Val--Tyr--Val--His--Pro--Phegly--OBu^(t)

6.6 Milliliters (0.052 mol) of N-ethyl morpholine were added at 0° C to a solution of 27.4 g (0.028 mol) of H--Val--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t) in 200 ml of dimethylformamide. After addition of a solution of 16.5 g of Z₃ Arg--OH and 3.4 g of 1-hydroxy benzotriazole in 100 ml of dimethylformamide, the mixture was cooled to -5° C. A solution of 5.9 g of dicyclohexyl carbodiimide in 15 ml of dimethylformamide was admixed while stirring. Stirring was continued for 1 hour at 0° C and for 12 hours at room temperature. The separated dicyclohexyl urea was filtered off, and the solvent was removed by distillation in vacuo at room temperature. The remaining oily substance solidified on trituration with 2N Na₂ CO₃ solution and water.

Yield: 38.7 g, m.p. decomposition beginning at 135° C, [α]_(D) = -6.8° (C = 1, DMF).

m. H--Arg--Val--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t) . 3 HCl

A solution of 37.5 g of Z₃ Arg--Val--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t) in 1.3 l of methanol was hydrogenated and worked up as disclosed sub (f).

Yield: 28.2 g, m.p. 143° C (decomposition), [α]_(D) = -7.2° (c = 1, CH₃ OH).

n. Succinamoyl--Arg--Val--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t)

2.56 Grams (0.024 mol) of H--Arg--Val--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t) . 3 HCl were dissolved in 26 ml of dimethylformamide at 0° C, and 0.91 ml (0.0075 mol) of N-ethyl morpholine was added. After addition of a concentrated solution of 324 mg of N-hydroxy benzotriazole (0.0037 mol) and 420 mg of succinic acid mono-amide in dimethylformamide, the mixture was cooled to -5° C while stirring, and a solution of 545 mg (0.0026 mol) of dicyclohexyl carbodiimide in 5 ml of dimethylformamide was added. Stirring was continued for 1 hour at 0° C and for 12 hours at room temperature. Separated dicyclohexyl urea was then suction-filtered, and the filtrate was concentrated in vacuo at room temperature to yield an oily residue which solidified upon trituration with dry diethyl ether. The product was washed with 2N Na₂ CO₃ solution and water and dried in vacuo.

Yield: 3.4 g (crude), m.p. starting at 100° C, [α]_(D) = -7° (c = 1, DMF).

o. Succinamoyl--Arg--Val--Tyr--Val--His--Pro--Phegly--OH

2 Grams of succinamoyl--Arg--Val--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t) were dissolved in 20 ml of 90% trifluoroacetic acid, and the solution was stirred for 60 minutes. The trifluoroacetic acid was distilled off in vacuo at 25° - 30° C, the residue was triturated with dry diethyl ether, dissolved in 100 ml of 90% methanol and passed through 40 ml of Amberlite IR 45-acetate form in a column having a diameter of 1 cm. The column packing was washed with 250 ml of 90% methanol, and the combined solutions were concentrated to dryness in vacuo at room temperature. The residue was triturated with dry diethyl ether and dried in vacuo.

Yield: 1.4 g. The crude product was purified by partition chromatography on Sephadex LH 20.sup. (R) (column size: 2.5 × 100 cm) in the solvent system n-butanol/acetic acid/water (2:1:10). 350 mg of crude product yielded 160 mg of a chromatographically pure product; m.p. 221° C (decomposition); [α]_(D) = -38.2° (c = 1, CH₃ OH). After a 72-hour hydrolysis using 6N HCl at 110° C, amino acid analysis showed the following ratios:

Arg: 0.80, Val: 2.00, Tyr: 0.87, His: 0.91, Phegly: 1.02. Pro was not determined.

EXAMPLE 2 a. Boc--Sar--Arg--Val--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t)

1.24 Grams (0.001 mol) of H--Arg--Val--Tyr(Bu^(t))--Val--His--Pro--Phegly--OBu^(t) . 3 HCl were dissolved in 10 ml of dimethylformamide and at 0° C 0.380 ml of N-ethyl morpholine was added while stirring. A solution of 0.55 g (1.5 mmols) of Boc-Sar-OTCP* in 2 ml of dimethylformamide was added, and 135 mg (1.0 mmol) of N-hydroxy benzotriazole were admixed. Stirring was continued for 1 hour at 0° C and for 20 hours at room temperature when the solution was concentrated to dryness at room temperature in vacuo. The residue was triturated with dry diethyl ether and dissolved in ethyl acetate. The solution was washed with sodium carbonate solution and water, dried over sodium sulfate, and the product was isolated as a colorless, amorphous powder by distilling off the ethyl acetate and triturating the residue with ether.

Yield: 1,3 g, m.p. 142° C, [α]_(D) = -15.8° (c = 1, DMF).

b. H--Sar--Arg--Val--Tyr--Val--His--Pro--Phegly--OH

1.7 Grams of the aforementioned, protected sarcosine peptide were dissolved in 10 ml of 90% trifluoroacetic acid, and the solution was stirred for 50 minutes at room temperature. The solvent was then distilled off in vacuo at room temperature, and the residue was triturated with 100 ml of dry diethyl ether. 1.0 Gram of a colorless, amorphous powder was obtained, which was dissolved in 20 ml of 90% methanol and passed through 10 ml of Amberlite IR 45 (acetate form). Another 250 ml of 90% methanol were passed through the column, and the combined solutions were dried in vacuo at room temperature. The remaining residue was dissolved and precipitated several times from ethanol/ether.

Yield: 748 mg, m.p. 166° C (decomposition), [α]_(D) = -20.5° (c = 0.5, DMF/H₂ O 1 : 1).

Partition chromatography on Sephadex LH 20 in the solvent system butanol/acetic acid/water (2 : 1 : 10) yielded the chromatographically pure end product, m.p. 225° C.

[α]_(D) = -25.0° (c = 0.5, DMF/H₂ O, 1 : 1).

After a 24-hour hydrolysis using 6N HCl at 110° C, amino acid analysis was as follows:

Sar: 0.9, Arg: 0.85, Val: 1.99, Tyr: 0.80, His: 0.88, Phegly: 1.0. Pro was not determined. 

We claim:
 1. A peptide derivative of formula I

    y--arg--Val--Tyr--Val--His--Pro--Phegly--OH                (I)

in which Y stands for the sarcosyl, succinamoyl or succinoyl radical.
 2. A pharmaceutical composition suitable forthe diagnosis and/or treatment of hypertonia, which comprises an effective amount of a compound as claimed in claim 1, optionally in admixture or conjunction with an inert carrier and/or preserving agent.
 3. A pharmaceutical composition having prolonged duration of action in the treatment of hypertonia, which comprises an effective amount of a compound as claimed in claim 1 in the form of a complex compound with zinc and, optionally, with phosphate ions.
 4. A pharmaceutical composition having prolonged duration of action in the treatment of hypertonia, which comprises an effective amount ofa. a compound as claimed in claim 1, b. a gelatin derivative cross-linked with hexamethylene isocyanate, and c. polyphloretin phosphate. 